Air conditioning



Feb. 13, 1940. e. v; WOODLING AIR CONDITIONING Original Filed April 22, 1932 Sheets-Sheet 1 PSYCHROMETSIC CHART WI EFFECTIVE TEMPERRTURE LINES FOR STILL HIR CONDITIONS RSONS NORMRLLY CLOTHED AND SLIGHTLY ACTIVE A. S. H. V. E. Research Labor tory U 5 Bureau of Mines Pittsburgh, Pa.

Dry 50gb Tempcr'a J00 tuna f WITH CTIVE TEMPERRTU RE LINES HIR VELOCITY 0F 30 PERSONS NORMHLLY C 0 FT. PER MIN. LOTH ED AND SLIGHTLY ACTIVE A. S. H.V. E.

R search Laborqtory U.S. Bureau of Mlnes Pi Hsburg h, Pa.

I INVENTORQ 70 so '90. I00

D, bulb temperature ATTORNEYS Feb. 13, 1940. G. v. WOODLING 2,190,344

AIR CONDITIONING Original Filed April 22, 1932 5 Sheets-Sheet 2 1319 3 Re/afhre Humidif s 1 Differential Empem zure Sea/e Dry Bulb Wet Bulb Dry Bulb Empera. fare Scale Wet Bulb Temperature Scale Effective Temperature Scale Di fferen iz'a 73/11 5/4 iures y p DryBulb-Wet Bulb I0 3036' D q 5 N v) U 3 u, 2 /s V o L 6 a Q2 1. u: U

0 I0 20 3o 40 Differenlm/ Fmpemfures LZLy 6 200 I w: S, Radia/ Distances 40 g Linear Units as A '2 X r i in subtracted fi'omDryBu/b L marked Off an N cmpcmiures to a! Eff i ve C scale EF Temperatures :9 e I k 7/ INVENT OR.

BY WMW $4;

ATTORNEYS Feb. 13, 1940. s. v. WOODLING AIR CONDITIONING Original Filed April 22, 1932 5 Sheets-Sheet 3 Web Bulb Dry Bulb flnemometer Sh'aft by; INVENTOR. 1 v

/ 8 ,Mwn 514 ATTORNEYS Feb; 13, 1940. G. v. wboDuNs 2,190,344

AIR CONDITIONING 7 Original Filed April 22, 1932 Sheets-Sheet 4 c mm Plane of Light. Retain/e Humidity l l l Graph Member 20 3b 4 0 so do nub) Relative Humidity W I 4 3a J L k Q so Different/(1L 6O 7 0 Wet Bulb 80 Effective Emperatuze -Dry Buie Values for the Illustrated Positions Dry Bulb Temperafure 90 2. Wet Bulb Tmperaiure 72 3. Differential Tempera for: /8 4. Eelaive Humidity 4 5 Effective Emperature 41 1/ INVENTOR. f?

ATTORNEYS Feb. 13, 1940.

J0utside G. V. WOODLING AIR CONDITIONING Original Filed April 22, 1932 5 Sheets-Sheet 5 para for:

4sa 7: a0 outslde Effectlvc Temperatura Desirable Indoor Em erafiure 01 Summer Compared To Outside Temperature Deqrees Deqrees Outside Inside.

'D.B. VV-B. ET 115. W.B. E1?

75 64 In; 73.5 63 61-3 70 b2 67 72 62.5 69.2.

INVENTOR.

ATTORNEYS Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE AIR CONDITIONING Delaware Original application December 3, 1932, Serial No. 645,570, which is a division of application Serial No. 606,837, April 22, 1932.

Divided and this application November 10, 1936, Serial No.

2 Claims.

My invention relates, in general, to air conditioning, and more particularly to means for measuring the condition of the air.

This application is a divisionof my application b for Letters Patent, Serial No. 645,570, filed December 3, 1932, now Patent No. 2,166,697 dated July 18, 1939, which is a division of application Serial No. 606,837, filed April 22, 1932, now Patent No. 2,139,297 dated December 6, 1938,.

An object of my invention is to provide for measuring the relative humidity and the effective temperature of air.

Another object of my invention is to give a measurement that is a true index-oi a person's I 16 feeling of comfort or discomfort in all combinations of the dry-bulb, temperature, the relative humidity and the air velocity.

A further object of my invention is to translate three movements into a single resultant move- 20 ment.

A still further object of my invention is the provision of a psychrometric device that measures the effective temperature in all combinations of the dry-bulb temperature, the relative 5 humidity, and the air velocity.

Another object of my invention is the provision of a psychrometric device that is responsive to the dryand wet-bulb temperatures for measuring the relative humidity.

It is also an object of my invention to provide for regulating theeffective temperature of the air in a building, or in an enclosure, in accordance with the effective temperature of the air on the outside of the building or the enclosure.

It is a further object of my invention to cause the movements of the psychrometric device to I vary the amount of light falling upon a photoelectric cell for controlling the air-conditioning ecuipment, the heating apparatus, or the hu- 40 midifying equipment.

A still further object of my invention is the combination of a psychrometric device and photo-electric cells, together with suitable amplifying circuits, for controlling the air conditioning equipment, the heating apparatus, or the humidifying equipment to give the maximum degree of comfort.

Another object of my invention is to provide 5 for so regulating the dry-bulb temperature that,

for any change in the relative humidity or the air velocity which results in a change in the effective temperature, a correction is made in the dry-bulb temperature to offset the said change in the effective temperature caused by method for determining the relative humidity 1 from the dry-bulb and wet-bulb temperatures.

Fig. 4 is the graphica representation of a method for determining the effective temperature for all combinations of dry-bulb temperatures, wet-bulb temperatures, and air velocities. N

Fig. 5 is a graph showing the relationship between the linear displacement plotted against the numerical values, as marked oif on the line CD of Fig. 4, I

Fig. 6 is a graph showing the relationship be- 25 tween the linear displacement plotted against the numerical values, as marked off on the line EF 01! Fig. 4,

Fig. 'Zis a plan view partly in section of a psychrometric device that measures both the 80 relative humidity for all combinations of dryand wet-bulb temperatures, and the effective temperature for all combinations of the dryand wet-bulb temperatures, together with the air velocities, 85

Fig. 8 is a rear elevational view of the psychrometric device, shown in Fig. '7,

Fig. 9 is a view taken along the lines a-b of Fig. '7, part of the elements being omitted to clarify the view, as well as to explain the relative 40 angular displacements of the various parts,

Fig. 10 is a front elevational view of the psychrometric device shownin Fig. 7, and illustrates indicating hands for the dry-bulb temperature, the wet-bulb temperatures, the eifec- 45 tive temperature, and the relative humidity, together with graph-members based upon the effective temperature and the relative humidity,

Fig. 11 is a diagrammatic view of two fundamental circuits that may be associated with two psychrometric devices for regulating the eflective temperature of the air inside of a building in accordance with the effective temperature of the air surrounding the building,

Fig. 12 is a graph, together with a chart upon system wherein the electro-magnets that operate the air conditioning equipment may be operated by a control circuit employing grid-controlled glow-discharge tubes, such as the circuit shown in Fig. 14.

The effective temperature is an experimentally determined scale, and therefore represents the true index of a person's feeling of warmth in all combinations of temperature, humidity, and air motion.

The temperature sensations of the human body depend not only upon the temperature of the surrounding air as registered by a dry-bulb thermometer, but also upon the temperature as indicated by the wet-bulb thermometer, together with the air motion. Human comfort or discomfort, as regards feeling of warmth, depends largely upon the body temperature, and, therefore, upon the relation between the rate of proe duction and dissipation of heat.

By the process of metabolism heat is constantly generated within the body, which heat must be eliminated from the surface of the body and from the respiratory tract by radiation, convection and evaporation. Hence, to maintain a constant body temperature the heat loss must equal the heat produced. It is, therefore, apparent that any reduction in the elimination of heat from the body must result in a rise in temperature and a corresponding feeling of discomfort. As the temperature of the air and surrounding objects rise, the

loss of heat by convection and radiation decreases. When the air temperature reaches that of the body, the loss by radiation and convection ceases. Finally, as the air temperature exceeds that of the body, heat is transferred from the air to the body. As the temperature-of the air rises and heat loss by radiation and convection decreases, the body endeavors to maintain temperature equilibrium by making available more perspiration, thus resulting in a greater heat loss by evaporation.

From the foregoing, one notes that there must necessarily exist certain combinations of air temperatures, air humidities and air motions, which produce the same total heat loss from a person by radiation, convection, and evaporation which produce the same feeling of comfort or discomfort upon the person notwishstanding variations in one or more components of said combinations.

The combination of temperature, humidity and air movement which produces the same feeling of warmth are called thermo-equivalent conditions or effective temperature lines. Elaborate experiments show that this newly developed scale of thermo-equivalent conditions not only indicates the sensation of warmth, but also determines the physiological effects on the body induced by heat and cold. For this reason, the thermo-equivalent condition is generally referred to as the effective temperature scale or index.

Effective temperature is an experimentally determined scale which unlike the dry-bulb and wet-bulb scales is a true measure or index of a persons feeling of warmth in all combinations of temperature, humidity, and air movements. In other words, for any one given effective temperature a person feels the same degree of warmth or coldness regardless of the dry-bulb temperature, the wet-bulb temperature, and velocity of the air required to produce that particular effective temperature.

With reference to the two psychrometric charts of Figs. 1 and 2, the dry-bulb temperature is plotted as abscissae and the grains of moisture per pound of dry air as ordinates. The maximum moisture which the air can hold at various temperatures gives the saturation, or 100 percent relative humidity curve. Relative humidities between zero and 100 percent are given by a series of curved lines similar to the. saturation curve. The wet bulb temperatures for all atmospheric conditions are given by a series of nearly parallel oblique lines. Effective temperature is given by a series of oblique but not parallel lines which approach being parallel to the wet-bulb lines at high temperatures. In the psychrometric chart of Fig. 1, which is for still air, the effective temperature line is vertical and coincides withthe drybulb temperature line at 46.' In Fig. 2, which is for air moving at the rate of 300 feet per minute, the effective temperature line is vertical and coincides with the dry-bulb temperature line at 56. Although not shown, for air velocities of 100 and 500 feet per minute the effective temperature lines and the dry-bulb temperature lines coincide respectively at 51 and 50.'

For dry-bulb temperatures below these respective values, an increase in humidity produces a cooler sensation, instead of a warmer sensation as is produced for dry-bulb temperatures above these values. The values may be called the dividing lines at which humidity has no effect upon the comfort of the body.

The psychrometric chart of Fig. 2 for moving air, differs from the chart of Fig. 1 for still air only in that the effective temperature lines for any particular degree do not intersect the drybulb and wet-bulb temperature lines at the same degree on the saturation or 100 percent relative humidity curve, but are removed to the right so that the effective temperature for any dryand wet-bulb temperature is lower for moving air than it is for still air. effective temperature for still air and for moving air, of any velocity, is the cooling resulting from that velocity.

Referring to the psychrometric chart in Fig. 1, a dry-bulb temperature of 70 and a wet-bulb temperature of 54 produces an effective temperature of 65. This is for still air. Referring to Fig. 2, which is for air moving at the rate of 300 feet per minute, the same dryand wetbulb temperatures produce an effective temperature of 60, or a reduction of 5 resulting from a change in air velocity.

For winter-time conditions in relatively cold climates, and for persons normally clothed and slightly active, extensive tests show that the comfort zone ranges from an effective temperature of 62 F. to an effective temperature of 69 F. That particular effective temperature at which a maximum number of people feel comfortable is called the comfort line. While at rest, 97 percent of the people have been found to be comfortable at an effective temperature of 64 F., and this temperature is generaly considered as the winter comfort line or optimum effective-temperature.

I-Iowever, persons working at various rates are and Ventilating Engineers from 1923 to the pres-- ent date by F. C. Haughten and C. P. Yaglou.

Since one of the purposes of the psychrometric device is to measure the eifective temperature, it follows that its functioning must be based upon a useful and practical relationship that combines the dry-bulb temperature, the relative humidity, and the air motion. From a study of the psychrometric charts of Figs. 1 and 2, together with other psychrometric charts (not shown), I find that by reorganizing the foregoing values upon a different basis, a useful and practical relation results. Such a relationship is shown in Fig. 4. In this relationship, however, the relative humidity is not considered directly, but by its derived value, as determined by the dry-bulb and wetbulb readings.

In Fig. 4, the dry-bulb temperature is scaled off on the line OY; the amount to be subtracted from the dry bulb to equal the efiective temperature on the line OX; the difierence between the dry-bulb and the wet-bulb temperatures on the line CD; and the air velocities on the line EF.

The air velocity line, EF, is determined as follows: With reference to the psychrometric chart of Fig. 1, which is for still air, one observes that, at a dry-bulb temperature of 46, the amount to be subtracted from the dry-bulb temperature to equal the effective temperature is zero. This establishes the zero point on the line EF. Similarly, with reference to the psychrometric chart of Fig. 2, which is for an air velocity of 300 feet per minute, one observes that, at a dry-bulb temperature of 56,the amount to be subtracted from the dry-bulb temperature to equal the effective temperature is 10. This establishes the point Elilll on the line EF. The points for air velocities of 100, 206, 400 and 500 may be established in a similar manner.

The line CD is likewise empirically established by first plotting a family of lines which have for their base the line EF and which converge at a dry-bulb temperature of 120 F. The values for plotting the family of lines are obtained from the psychrometric charts of Figs. 1 and 2, together with other similar charts (not shown). For instance, the line G, interconnecting the zero point on the line EF and the point 5 on the line CD- is determined by establishing a series of points. the values of which being obtained from the psychrometric chart of Fig. 1, and drawing a line through the said points. With reference to Fig. 1, which is for still air, we observe that, at a drybulb temperature of 75 F. and a wet-bulb temperature of F. (a difference of 5?), the effective temperature is 727 F. This means that, at a dry-bulb temperature of F. and with a difference of 5 between the dry-bulb and the wet bulb temperatures, the amount to be subtracted from the dry-bulb temperature to equal the corresponding effective temperature, is 2.3. Therefore, with reference to Fig. 4, a dry-bulb temperature of 75 F., as measured on the line and a value of 23, as measured on the line OR, established a point it" for the line G. For the point i, on the line G, we observe from Fig. 1 that the amount to be subtracted from a drybulb temperature of F. (with a wet bulb temperature of 95 F.), to equal the corresponding effective temperature, is 4. Similarly, for the point 5, being the point where the line G intersects the line CD, we observe from Fig. 1 that the amount to be subtracted from a dry-bulb temperature of 120 F. (with a wet-bulb temperature of F.), to equal the, corresponding effective temperature, is 5.5.

Other points for establishing the position of the line G may be determined in the same manner. As will be noted, the established points for the line G lie in a straight line.

The other lines interconnecting the zero point on the line EF and the points I0, 20 and 30 on the line CD may be established in the same manner as the line G was established, except that the differences between the dry-bulb temperatures and the wet-bulb temperatures are 10, 20 and 30, respectively.

The family of lines interconnecting the point 300 on the line EF and the points 5, l0 and 20 on the line CD may also be established in a similar manner, except that the values for establishing these lines are taken from the psychrometric chart in Fig. 2, which is for an air velocity of 300 feet per minute. The values for determining the family of lines interconnecting the points I00 and 300 on the line EF and the points 5, HI and 20 on the line CD are taken from psychrometric charts (not shown) for air velocities of 100 and 500 feet per minute, respectively. As will be observed, all of these lines are substantially straight, except those for the higher air velocities, and they may, for all practical purposes, be considered straight. While I have drawn the foregoing family of lines to explain the method as to how they are established, it is readily apparent that an infinite number of such lines may be drawn. From the reserves that the family of lines converge at F., thus indicating that at this high temperature the air velocity has no cooling effect upon the body. Therefore, when the chart in Fig. 4 is once-established, we can obtain from it the amount to be subtracted from the dry-bulb temperature to equal the corresponding effective temperature for all possible combinations of dry-bulb temperature, wet-bulb temperatures and air velocities. As will appear later, that part of the psychrometric device for measuring the effective temperature is based upon the chart of Fig. 4. However, before describing the structural features of the organized psychrometric chart of Fig. 4, one obpsychrometric device, I will explain the basis for directly determining the relative humidity from the dry-bulb and wet-bulb temperature readings.

With reference to the chart in Fig. 3, the drybulb temperature readings are sealed off on the arcuate line JK; the difference between the drybulb and the wet-bulb temperatures on the arcu ate line LM; and the relative humidity on the straight horizontal line LN. The angular position of the arcuate line LM relative to the arcuate line JK is determined by making the zero or starting point of the line LM and the dry-bulb temperature reading of 60 on the line JK lie on the same radius; namely, the line OPL. The radial position'of the arcuate line JK relative to the arcuate line LM is such that the distance OP equals two-thirds of the radial distance OL. However, any other ratio may be employed so long the proper considerations of all the factors effecting the ratio are taken into account. As illustrated, the dry-bulb temperature readings, as marked off on the arcuate-line JK, range from 46 to 120 F., and the differential readings, as marked off on the arcuate line LM, range from 0 to. 35. These temperature readings correspond to those shown in Fig. 4, and are more than adequate to accommodate any and all possible heating and air conditioning requirements. The relative arcuate lengths of the dry-bulb temperature scale JK and the differential scale LM may bear substantially the same proportion as shown. However, should it be desirable to reduce the length of the relative humidity scale LN, this may be done by reducing the arcuate length of the differential scale LM relative to the arcuate length of the dry-bulb temperature scale JK. Both the position and the readings, as marked off on the relative humidity line LN, are established empirically by drawing intersecting lines through the dry-bulb temperature scale JK and the differential scale LM. vReferring again to the psychrometric chart of Fig. 1, we observe that a dry-bulb temperature of 70 and a wet-bulb temperature of 59 (a difference of 11) give a relative humidity of 50 percent, and that a drybulb temperature of 100 and a wet-bulb temperature of 84 (a difference of 16) likewise give a relative humidity of 50 percent. Hence, the intersection of a line drawn through 70 on the scale JK and 11 on the scale LM with a line drawn through 100 on the line JK and 16 on the scale LM determines the point for 50 percent relative humidity. Similarly, the intersection of a line drawn through a 70 on the scale JK and 14 on the scale LM with a line drawn through 100 on the scale JK and 20.5 on the scale LM determines the point for 40 percent relative humidity. As illustrated, other points for the relative humidity line LN may be determined in a similar manner. I find that, by plotting the chart shown in Fig. 3 on a large scale the working range of the relative humidity scale LN is very accurate. However, there is a slight percentage of error at the extreme ends of the scale.

That part of the psychrometric device for measuring the relative humidity is based upon .the chart in Fig. 4. As far as it is possible to do so, the twoparts will be described separately, even though structurally they are'mutually dependent. I will describe the part concerning the relative humidity first.

With particular reference to Figs. 7, 8, 9 and 10, the reference characters 500 and 50l represent two rotatable shafts, the rotation of which are, respectively, responsive to the dryand wet-- bulb temperatures. Several methods, well known in the art, are available for operating the dry.- and wet-temperature shafts, but, since this constitutes no part of my invention, I have omitted making a showing of such. a means. Generally, such a means may comprise a tube containing a thermo-expansive fluid connected to a Bourdon tube helix which expands and unwinds in a well known manner to rotate the said shafts. For

the dry-bulb temperature shaft 500, the tube that contains the thermo-expansive fluid is exposed to the ordinary atmosphere and for the wet-bulb temperature shaft 50l, the tube may be either surrounded with a wick dipped into a tank of water or any other means to efl'ect an evapora-. tion. Also, as a modification, the dryand wetbulb shafts 500 and 5M may be remotely controlled by anelectrical means that is responsive to a dryand a wet-bulb thermometer.

As illustrated, the dryand wet-bulb temperature shafts are rotatively mounted in brackets 502 which are supported by a base member 503. Through a transmission of the planetary type, the two shafts are arranged to operate a drybulb temperature hand 505 and a differential temperature hand 506. As shown in Fig. 10, the dry-bulb temperature scale JK, the differential temperature scale LM, and the relative humidity scale LN provided upon the face 509 of the psychrometric device are constructed upon the same basis as the chart shown in Fig. 3. The effective temperature hand is represented by the reference character 50! and the wet-bulb temperature hand by 508. Their values are read off on the dry-bulb temperature scale JK.

The dry-bulb temperature shaft 500 extends through the various parts of the psychrometric device and the dry-bulb temperature hand 505 is connected upon the outer or right-hand end thereof. Surrounding the dry-bulb temperature shaft 500 is a hollow or tubular shaft 5l0, and the differential temperature hand 506 is connected tothe outer or right-hand end thereof and the rear or left-hand end thereof is connected to the differential transmission. Inasmuch as the linear arcuate unit for the differential scale LM is larger than the corresponding arcute linear unit for the dry-bulb temperature scale JK, the left hand end of the tubular shaft 5l0 is connected to the sun gear M2 and the dry-bulb temperature shaft 500 is connected through the usual spider to the planetary gears 5|3 of the differential transmission. The orbit gear 5 of the transmission is driven by the wet-bulb temperature shaft 50| through a gear wheel 5l5. In this manner, the difference in angular displacement of the dryand wet-bulb temperature shafts is transmitted through the sun gear 5l2 and hence the tubular shaft 5l0 to the difierential hand 506. The gear wheels of the planetary transmission are so proportioned that, for any reading of the dryand the wet-bulb temperature hands 505 and 508, as marked'oif on the scale JK, the differential hand 506 indicates a value, as marked off on the differential scale LM, that is the difference between the dryand wet-bulb temperature readings.

As illustrated, the relative humidity scale LN may be horizontally supported upon the face 509 by suitable pins 5I6 or their equivalents. The lower edge of the relative humidity scale is provided with a longitudinal slot in which a pin 5|! is disposed to be slidably mounted. Interconnecting the pin 5| I and the outer ends of the drybulb temperature hand 505 and the differential temperature hand 506 is a. slotted arm 5l8. Hence, as the dry-bulb temperature hand 505 and the differential temperature hand assumes different relative positions, the upper end of the slotted arm 5l8 constrains the pin 5i'l to move along the longitudinal slot of the relative humidity scale LN. The position of the pin 5I8 deter mines the relative humidity reading for the corresponding readings of the dryand wet-bulb temperatures. I

In the position as shown, the dry-bulb temperature hand 505 indicates a temperature of 90 upon the scale JK and the differential temperature of 18. For this position of the dry-bulb temperature hand 505 and the differential hand 506, the corresponding relative humidity reading is 40 per cent. This particular setting of the hands is also indicated on the chart shown in Fig. 3. The heavy line 505 represents the position of the dry-bulb temperature hand 505; the'heavy line 506 indicates the position of the differential hand 506 and the heavy line 5l'8 indicates the slotted arm 518. As is readily apparent, my psychrometric device provides for measuring the relative humidity for any and all possible combinations of dry-bulb and wet-bulb temperatures.

For the purpose of regulating the humidifying equipment of an air conditioning system, I provide a relative humidity graph-member 520 and a light projector II2 (see Figs. 10 and 13) for varying the amount of light falling upon a photo-.

electric cell III) of an amplifying circuit, which, in turn, actuates a pole changer relay 525 for controlling the polarity of the current delivered to the humidifying equipment. The amplifying circuit and the light projector II2 for accom plishing this result are shown in Fig. 13.

Two well known methods are available for varying the amount of light that passes through the light transmitting portion II4 of the graphmember 520. One may be termed the linear method, and the other the area method. With reference to the light projector II2, the linear method may be described as follows: The light projector II2 comprises, in general, a cylindrical housing H9 in which are disposed, at the left end, two condensing lenses I20 and, at the right end, two objective lenses I2I, and, in the middle, a transversely disposed member having a vertical narrow slit I22. By means of the condensing lenses I20 and the objective lenses I2I, and the slit I22, the light from the concentrated filament of the lamp III is formed into a plane of light. The intensity of this plane of light may be suitably varied by the adjustable resistor I45 that is connected in circuit relation with the source of electrical energy I42.

As shown, this plane of light is directed perpendicularly to the plane of the transversely disposed relative humidity graph-member 520. By reason of the demagnifying effect of the lenses the width of the plane of light at its focal point, being the point at which it passes through the light transmitting portion. III, is several times smaller than the width of the slit I22. breadth or the height of the plane of light is slightly greater than the maximum height; of the light transmitting portion II4. Therefore,

I the quantity of light falling upon the photo-electric cell III) is determined by the amount that the graph-member 520 is transversely moved relatively to the plane of light, or, in other words, by the height of the ordinate of the light transmitting portion H4.

The graph-member 520 may be constructed either of a thin sheet of opaque material or of a photographic film. When the graph-member 520 is constructed of a thin sheet of opaque material, the light transmitting portion I I4 takes the form of an aperture, but when a photographic film is used, the light transmitting portion II4 is transparent while the surrounding portion is dark. In the case of a photographic film it is essential that the degree of transparency be uniform) members must not exceed the illumination boundaries of a photo-electric cell.

The relative humidity graph-member 520 is connected to the upper end of the slotted arm ill and may be slidably mounted in any suitable 'manner with reference to the light source III The and the photo-electric cell III! of the amplifying circuit of Fig. 13. I With reference to the relative humidity graph-member 520, the vertical dotted line represents the plane of light. In order to make the showing of the hand of the psychrometric device as clear as possible, I have omitted the relative humidity graph-member 520 in Fig. 7. The base of the light transmitting portion of the relative humidity graph-member 520 is the same length as the relative'humidity scale LN and to every relative humidity value, as

device which, when connected to a circuit of the proper potential and when illuminated from a suitable source, passes a very small amount of current of the order of micro-amperes. photo-electric cell IIII comprises, generally, an anode Ill and a cathode II8 sealed within either an evacuated space or within a space filled with a gas at a very low pressure. The cathode II 8 is constructed of a material that has the property of liberating electrons when illuminated. By impressing a potential of the proper polarity and magnitude between the anode Ill and the cathode IIB, the liberated electrons move toward the anode 1, thus eifecting a passage of current in response to the light falling upon the cathode IIB. Throughout the usual range .of illumination, the current passed by a photo electric cell is directly proportional to the illumination.

As is well known in the art, the feeble current that is passed by a photo-electric cell may, by means of either thermionic amplifiers or by gridcontrolled glow-discharge tubes, be eifectively amplified to operate electrical meters and sturdy relays. Each type of amplification has certain distinct advantages over the other.

Under correct and proper operating conditions, the out-put of a thermionic amplifier is directly proportional to the light falling upon the photoelectric cell, whereas this ls not exactly true with grid-controlled glow-discharge tubes. However, with the proper circuits,- a fair degree of proportionality can. be obtained by utilizing grid-controlled glow-discharge tubes. By reason of the high degree of proportionality, the combination. of thephoto-electric cell and the thermionic amplifiers, provides a good light meter and may, therefore, be suitably adapted to give calibrated indications and to operate pilot relays.

Although there are many amplifying circuits utilizing thermionic amplifiers with either direct or alternating current, or with one or more stages of amplification, I have preferably illustrated in Fig. 13, a simple direct current thermionic amplifying circuit having only one stage of amplification. However, it is to be understood that I do not intend .to limit my invention to the illustrated embodiment.

The illustrated amplifying circuit of Fig. 13 comprises, in general, the thermionic tube H5 having a filament I3I, a grid I32, and a plate I33, a grid resistor I40, a grid potentiometer I for biasing the potential of the grid I32, relative to the filament I3 I a filament battery I34, a plate battery I35, and a grid potentiometer battery I36. The plate battery I35 and the grid potentiometer battery I38 are connected in series circuit relation so that the sum of their voltages,

The

except as modified by the grid potentiometer MI, is impressed across the anode II I and the cathode N8 of the photo-electric cell H0.

In operation, when no light is falling upon the photo-electric cell IIO, it passes no current, with the result that the grid I32 of the thermionic tube H5 is sufficiently negatively charged wih respect to the filament I3I, as determined by the setting of the grid potentiometer I4I, that the value of the impedance between the plate I33 and the filament I 3I is sufficiently high that very little, if any, plate current flows through the thermionic tube II5. However, when the photoelectric cell I I is illuminated, it passes a current for decreasing the impedance of the thermionic tube H5. The current passed by the photo-electric cell IIO flows from the positive terminal of the battery I35 through the winding of the relay 525, the relative humidity recording meter 526, conductors I I and I52, the anode II! and the cathode II8 of the photo-electric cell, a conductor I53, the grid resistor I40, the grid potentiometer MI, and to the batteries I36 and I35. The current flowing through the photo-electric cell IIO causes a voltage drop over the grid resistor I40 in such direction as to'cause the grid I32 to become less negatively charged with respect to the filament I3I, with the result that the impedance of the thermionic tube II5 de-- creases. A decrease in the impedance of the thermionictube II5 allows a plate current to flowfrom the positive terminal of the battery I35 through the winding of the relay 525, the recording meter 526, the plate I33 and the filament I3I of the thermionic tube, and to the negative terminal of the battery I35.

The amplifying characteristic of a thermionic tube is linear, except at the two extreme ends of the grid bias voltage. Therefore, inview of the fact that the response of the photo-electric cell is also linear, the quantity of current that flows through the plate circuit of the thermionic tube H5 is linear with respect to the amount of light falling upon the photo-electric cell I I0. Because of the linear amplifying characteristics of the thermionic tube, the current that flows through the coil of the relay 525 and the winding of the recording meter 526 is likewise directly proportional to the readings of the relativehumidity.

A spring 524 having an adjustment nut is adapted to bias the armature of the relay downwardly and thus oppose the magnetic force of the coil of the relay. The circuit connections for the contacts of the relay 525 constitute a pole changer such that, when the magnetic pull of the coil isgreater than the spring bias, the armature is in the raised position and a current of one polarity is delivered from the supply source to the humidifying equipment, and when the magnetic pull is less than the spring bias, the armature is in the lowered position and a current of the opposite polarity is delivered from the supply source to the humidifying equipment. When the armature of the relay is balanced, no current is delivered to the humidifying equipment. Inasmuch as the humidifying equipment constitutes no part of my invention, I have omitted making a showing thereof. Briefly, the operation of the humidifying equipment may be such that, when a current of one polarity is delivered thereto, the humidifying equipment responds to increase the moisture content of the surrounding air, and when no current or when a current of the opposite polarity is delivered thereo, the humidifying equipment responds to deliver no moisture content to the surrounding air. This means that, by adjusting the tension of the spring 524, the humidifying equipment may be so regulated as to maintain the relative humidity of the surrounding air at a predetermined selected value. Also, there will be described on the paper of the recording meter 526 a graph of the relative humidity readings.

In Fig. 14, I show a modified form of a relative humidity control circuit, in which power gridglow tubes 36I and 356 are employed to pass sufficient current to actuate a relatively large electromagnet 528 that may be mechanically connected to an operating valve 53I of the humidifying equipment. This circuit is substantially the same as the control circuit shown in Fig. 35 of my Patent No. 2,139,297, entitled Measuring and regulating devices, and like reference characters represent like parts, the only difference being that the power grid-glow tubes 36I and 366 deliver current to the electromagnet 528 instead of to the armature of the dynamo-elecric machine 350 and that the amount of light falling upon the photo-electric cell 395 is determined by the relative humidity graph-member 520 of the psychrometric device instead of the graph-member 40I of the electrical meter 394.

As illustrated, a relatively strong spring 530 hav- 7 ing an adjustment nut 529 is adapted to oppose the magnetic force of the electromagnet'528. As is apparent, this modified form of humidity control is very sensitive and, accordingly, the modulations or the variations from a normal or predetermined selected relative humidity value is reduced to a minimum. As illustrated, a recording meter 52! is connected in series circuit relation with the electromagnet 528 and thus a graph of the relative humidity readings will be described on the recording paper thereof. Therefore, from the foregoing, it is observed that my psychrometric device provides for measuring and recording the relative humility for any and all possible combinations of dry and wet temperature readings, as well as for so regulating the humidifying equipment of an air conditioning system that the relative humidity of the surrounding air is maintained at a predetermined selected value.

As illustrated, the inner end of the wet-bulb temperaturehand 508 passes through a suitable arcuate aperture 52I in the dial or face. 509 and is connected to the rim of a gear wheel 5| 9, which is rotatively and freely mounted upon the tubular shaft 5| 0 immediately in rear of the dial or face 509. The gear wheel 5I9 meshes with a gear wheel 520 that is mounted on the right end of the wet-bulb shaft 50I. The gear wheels 5I9 and 520 have the same diameters and, accordingly, any angular displacement of the wet-bulb shaft 50I is directly transmitted to the wet-bulb temperature hand 508.

As hereinbefore mentioned that part of the psychrometric device for measuring the efiective temperature is based upon the reorganized psychrometric chart of Fig. 4. In view of the fact that several ways may be employed to measure the efiective temperature, as based upon the chart in Fig. 4, I do not intend to be limited by the illustrated embodiment. In carrying out my invention, the principal object is to subtract a value (subtrahend) from the reading of the drybulb temperature (minuend) such that the remainder equals the efiective temperature. With reference to Figs. 7 and 9, I propose to perform this subtraction by utilizing the combination of a slidably mounted collar 555 having a cam 560 mounted thereon which engages a pin 562 that is carried by a second collar 56l to which the inner end ofthe effective temperature hand 501 is connected. As illustrated, the inner end of the effective temperature hand 501 passes through the arcuate aperture 52l in the dial or face 509 and thence through a suitably provided aperture in the web of the gear wheel 5l8 to the point where it is connected to the collar 56 I. As

shown in Fig. 9, a part of the tubular shaft 5l0 is slotted where the collar 555 is keyed by means of the key 556, or other suitable means, to the dry-bulb temperature shaft 500. In this manner, the collar 555 may move axially but is constrained to move angularly with the dry-bulb temperature shaft 500. Therefore, by axially moving the slidably mounted collar 555 to the right, the cam 560 engages the pin 562 and rotates the collar 56l that carries the effective temperature hand 501 backwards so that the effective hand reads a value less than the dry-bulb temperature hand 505 by an amount equal to the subtrahend. In other words, the axial displacement of the collar 555 and, consequently, the backward rotation of the collar 55! corresponds to the subtrahend values, as marked 011 on the line X of Fig. 4. Therefore, itremains to show how the axial displacement of the collar 555 is governed by the combination of the dry-bulb temperature, the differential temperature, and the air velocity. To this end, I provide a slotted arm 552, in which the upper end of a pin 551 that is connected to the collar 555 is disposed to slide when the dry-bulb temperature shaft 500 is rotated between the dry-bulb temperature readings of 46 and 120. The lower end of the slotted arm 552 is pivotally connected at a pivotpoint 510 to a slidably mounted member 548 that is actuated in accordance with the air velocity, and the upper end of the slotted arm 552 is actuated by a slide bar 553 that is governed in accordance with the differential temperature.

The slide bar 553' is carried by a suitable bracket 551 and the left end thereof is adapted to engage a cam 542 that is suitably mounted upon the periphery of a disc which may be keyed, or otherwise connected, to the tubular shaft 510. The shape of the cam 542 is based upon the graph in Fig. 5, which represents the relationship between the linear units,as marked off on the differential temperature scale CD of Fig. 4 and the-corresponding differential temperatures. Therefore, the upper end of the slotted arm 552 is actuated in accordance with the differential temperature. In the position as shown, the differential temperature is 18.

The lower end of the slotted bar 552 is actuated in accordance with the air velocity. The reference character 543 represents a shaft that is adapted to be rotated by an anemometer (not shown). For this particular application, the anemometer may be of the vane type, wherein the position of the vane is determined by the force or velocity of the air. No showing of the anemometer is included inthe drawings because it constitutes no part of my invention. The end of the anemometer shaft 543 is provided with a worm 545 which engages a worm wheel 545 that rotates a polar cam 541, all of which is carried by a suitable support 544. Extending outwardly at an angle equal to the angle that the line EF makes with the line OX of Fig. 4 is a bracket 550 having upwardly extending spaced ears in which the member 548 is slidably mounted. The lower end of the slidably mounted member 548 engages the periphery of the polar cam 541. A spring 549 disposed between the upwardly extending spaced ears and surrounding the member 548 is adapted to bias the lower end of the member 548 against the polar cam 541. The shape of the polar cam 541 is based upon the polar graph in Fig. 6, which represents the polar relationship between the linear units, as marked off on the line EF of Fig. 4, and the corresponding air velocities. Therefore, the slidably mounted member 548 may be moved in-and-out by the rotation of the anemometer shaft 543 so that the position of the pivot-point 510 corresponds to the air velocity values, as marked off on the line EF of Fig. 4. In the position as shown, the arm 552 may assume any one of an infinite number of positions and, at any one setting, it is analogous to one of the family of lines interconnecting the lines EF and CD of Fig. 4.

With reference to Figs. 3 and 9, the axial position of collar 555 is determined as follows: The arcuate line 5 of Fig. 3' is struck on the same radius as the circumference of the disc 5 of Fig. '7 and the pivot-point 510 is determined where the radius line S (corresponding to 46 DB) intersects the arcuate line 54! (Fig. 3) or the circumference of the disc 5 (Fig. '1); and the arcuate position of the slide rod 553 relative to the pivot-point 510 is determined by the insertion of the radius line T (corresponding to 120 DB) with the arcuate line 54! (Fig. 3) or the circumference of the disc 54I (Fig; '7). In the position, as indicated, the pivot-point 510 there fore represents a dry-bulb temperature of 46 and the positionof the slide rod 553 always represents a dry-bulb temperature of 120. The pin 551 is positioned at a dry-bulb temperature of 90 by shaft 500 and collar 555. Also the intersection of the radius lines V (or 0 differential) and W (or 35 differential) with the arcuate line 5 (Fig. '7) or the circumference of the disc 54! determines the arcuate length of the cam 542. In the position as shown, the disc 5 has been rotated by the shaft 5I0 in a clockwise direction to the point where a differential temperature of 18 on the cam 542 coincides with the engaging end of the slide rod 553. Therefore, the slidably mounted collar 555 isa-xially actuated to the right to such a position that the cam 550, in combination with the pin 552 and the collar 56l, retracts the effective hand 501 an angular distance equal to This means that with a drybulb temperature of 90, and a wet-bulb temperature of 72 (a difference of 18) the effective 1 temperature is 80, or 10 less than the dry-bulb temperature reading.

.Depending from the collar 55! is an effective temperature graph-member 564. The light transmitting portion of the effective temperature graph-member 564 has an arcuate base line with effective temperature readings ranging from.46 to 120 and to every value of the temperature reading there corresponds an ordinate of equal value. In the position as shown in Fig. 10, the plane of light is represented by the dotted line and it is passing through the'light transmitting portion at an effective temperature reading of 80. A spring 555 is connected to this graph-member in order to bias the effective hand in a clockwi e control current delivered to the air conditioning equipment, the condition of the air in a building may be maintained at a predetermined selected effective temperature.

In theatres and department stores, which are cooled artificially in Warm weather, the contrast between the outdoor and indoor'air conditions,

becomes the deciding factor in regard to the most desirable effective temperature to be maintained in the inside of the building. The object of cooling theatres in the summer is not to reduce the effective temperature to the optimum value, but to maintain therein a reasonably comfortable effective temperature and at the same time to 1 avoid sensations of chill or of intense heat in entering and leaving the building. The relationship between desirable indoor effective temperature in summer corresponding to various outdoor effective temperatures is plotted in Fig. 12. The effective temperature values for the curve in Fig. 12 are listed in the chart immediately below the figure. All of these values listed in the chart, except those for the outside effective temperatures, were taken from a table appearing on page 82 of the 1931 edition of the American Society of Heating and Ventilating Engineer's Guide. The values appearing in the outside effective temperature column were taken from the psychrometric chart in Fig. 1, using the corresponding outside dryand wet-bulb temperatures with the same number of grains of moisture per pound of dry air. It is noted that the effective temperature values for the curve in Fig. 12 substantially define a straight line and for all practical pur- I poses it may be considered as such, and that the higher the effective temperature on the outside, the higher the corresponding effective temperature on the inside. Therefore, from the foregoing, we observe that the control circuits which regulate the air conditioning equipment must be ing. The upper amplifying circuit is responsive to the outside effective temperatures and the plate current that flows through the coil 580 is disposed to exert a force that opposes the force set up by the plate current that flows through the coil 582, which is responsive to the inside effective temperatures. The spring 585 having an adjustment nut is likewise arranged to oppose the magnetic force of the coil 582. As illustrated, an adjustable resistor 58! is connected in shunt with the coil 580, so that the magnetic force of the coil 580 is relatively weak as compared to the magnetic force of the coil 582. The relative values of the magnetic force of the coils 580 and 582, together with the spring force, are such that, for example, with an outside effective temperature of 68.2 and with an inside effective temperature 67 the armature of the relay is balanced and the air conditioning equipment is inoperative. However, should the outside effective temperature rise, the balanced condition of the relay is disturbed, because the amplifying circuit that is responsive to the outside air conditions passes more current to increase the magnetic pull of the coil 580. This causes the air conditioning equipment to respond until the inside effective temperature is raised to a point where the armature of the relay again. becomes balanced. In other words a change in the outside effective temperature causes such a change in the inside effective temperature that the relationship conforms substantially with the curve shown in Fig. 12, or with any other desirable relationship which gives the most comfortable feeling.

As illustrated, a recording meter 583 and a recording meter 584 may be employed to record the outside and inside effective temperature readings, respectively.

In Fig. 15, I show a fragmentary view of a. modified form of the effective temperature control circuits, in which two power grid-glow tube circuits, such as the one illustrated in Fig. 14, may be employed to operate a valve 592, or other control means of the air conditioning equipment, by means of two electro-magnets 590 and 59l directly connected thereto, which are energized by the power grid-glow tubes. Also two recording meters 593 and 594 may be utilized to record, respectively, the outside and inside effective temperatures.

Inasmuch as the effective temperature is a measure of any and all possible combination of the dry-bulb temperature, the relative humidity, and the air velocity, the effective temperature control circuits of Figs. 11 and may regulate any one of the three factors while the other two may be allowed to vary uncontrolled. For example, if the control circuits of Figs. 11 and 15 are arranged to regulate the dry-bulb temperature only, the relative humidity and the air velocity may vary uncontrolled, because the drybulb temperature remains at the same predetermined selected value. In other words, my effective temperature control system is such that, for any change in the relative humidity or the air velocity which results in a change in the effective temperature, the dry-bulb temperature is corrected to offset the said change in the effective temperature caused by the change in the relative humidity and the air velocity. Therefore, even though the relative humidity and the air velocity may vary uncontrolled, the effective temperature is maintained at a predetermined selected value. In those cases where the air velocity is held constant, it is not necessary to use an anemometer, but the position of the slidably mounted member 548 may be adjustably set, by a set screw or other suitable means, at values that correspond to the predetermined selected constant air velocity.

It is to be pointed out that the amplifying circuits used through my invention are merely illustrative and, accordingly, they may take other forms. In the illustrated forms, the constancy or calibration of the circuits remain very accurate over a reasonable length of time, which is usually at leasta year or more and this condition will improve with the manufacture of better tubes. However, should the operating conditions require that no change in the calibration take place over .a period of several years, a null method may be employed, which counterbalances any change in the calibration.

Since certain changes in my invention may be made without departing from the spirit and scope thereof, it is intended that all matters contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. The combination of control means, a relay for operating said means, a light sensitive device, circuit connections interconnecting the relay and the light sensitive device, means emitting a plane of light, an opaque member having a light transmitting portion with at least two non-parallel sides for governing the amount of said light falling upon the light sensitive device, and condition responsive means for actuating the member, the non-parallel sides of the light transmitting portion being so proportioned that the magnitude of the plane of light falling upon the light sensitive device corresponds to the magnitude of the condition.

2. The combination of actuating means, a light sensitive device operatively connected to said actuating means, means emitting a plane of'light, a member having a light transmitting portion with at least two non-parallel sides for governing the amount of light falling upon the light sensitive device, means for actuating said member, the non-parallel sides of the light transmitting portion being so proportioned that the magnitude of the light falling upon the light sensitive device corresponds to the movement of said member.

GEORGE V. WOODLING. 

